We are studying the development of the hypothalamic-pituitary-gonad axis. We have developed a bovine Sertoli cell culture system. We have raised antibodies to luteinizing hormone releasing hormone in rabbits. These antisera have been partially characterized as to specificity, antibody titer and biological blocking activity. Patients in remission from acute lymphocytic leukemia and Ewing's sarcoma had hypothalamic pituitary testing. Abnormalities in the regulation of GH secretion have been demonstrated in patients who received prophylactic cranial radiation and have leukoencephalopathy as diagnosed by computerized axial tomography scan. Our studies on cystinotic patients have revealed a consistent defect in the hypothalamic-pituitary-thyroid axis. We have also developed normal values of the pulse-wave arrival time (Qkd interval) in children.